Comprehensive study of diesel engine characteristics of valves coated by titanium nitride (TiN)

Abstract

Nano-structured coatings have been used to simulate adiabatic engines with the aim of not only reducing heat rejection and thermal fatigue protection of the metallic surfaces but also potentially reducing internal combustion engine emissions. With this research work, the main emphasis is on optimizing the best coating thickness and studying the effects of nano-structured coatings on the engine's fuel consumption and thermal efficiency with the support of varying conditions. Emission measurements of hydrocarbon (HC), nitrogen oxide (NOx), and carbon dioxide (CO2) were also conducted in this study. In this study, the inlet and exhaust valves were coated with titanium nitride (TiN) material, using a magnetron sputtering technique. TiN was deposited at different thicknesses, such as 2, 3, 4, 5, and 6 microns, over the whole surface of the internal and exhaust valves. The results showed that the brake thermal efficiency (BTE) and NOx emissions were increased, and the specific fuel consumption, CO, and HC emissions were decreased for the thermal coated exhaust valve compared to the standard engine. Peak cylinder pressures for 4 µm thick coatings increased by up to 8.30% in the thermal barrier coating (TBC) engine, particularly at high power outputs; however, exhaust gas temperatures were generally lower, indicating noble gas expansion in the power stroke that initiated the peak cylinder pressure rise and impacted BTE, which increased by 1.6%. The result demonstrates that the TiN coating on the valve serves superior performance to the engine up to an optimum coating thickness beyond which the performance drops off. The characteristics are examined by using an experimental setup and measuring experimental values from the setup for different conditions.